In Disko Bay in Western Greenland the mesozooplankton biomass is dominated by Calanus spp. In this area the Atlantic Calanus finmarchicus, and the Arctic lipid rich C. glacialis and C. hyperboreus co-exist. During spring 2008 the grazing activity, reproduction, condition and distribution of the three Calanus species was investigated. C. finmarchicus commenced feeding as soon as phytoplankton was available, and approximately 2 weeks before initiated egg production. C. glacialis commenced feeding at the same time but initiated egg production almost immediately. The egg production per female and number of spawning females was higher for C. glacialis than C. finmarchicus over the course of the spring bloom. This could indicate that C. glacialis is more adapted to unpredictable bloom conditions compared to C. finmarchicus who needs food to initiate spawning. Contradictory to earlier believes, C. finmarchicus and C. glacialis filled their lipid stores while spawning during the bloom. These results stress the importance of timing of their vertical migration in relation to the spring bloom initiation. A possible mismatch would likely affect the spawning rate and lipid accumulation for subsequent diapause.